The invention relates to an apparatus for mounting workpieces, preferably discoidal substrates, in a vacuum chamber for the purposes of a surface treatment, especially for reactive ionic etching or coating by cathode sputtering.
In a known apparatus of the kind in question the substrate is, in a first phase, deposited on a substrate support in a special loading and unloading station disposed in the vacuum chamber, the substrate support being disposed at the free end of an arm that is mounted so as to pivot about a vertical axis. In a second phase, the arm then advances the substrate together with the substrate support into the range of the ion source or of the cathode. After the surface treatment has been performed, the arm is then swung back, in a third phase, to the loading station where the substrate is lifted from the substrate support by a suction cup and delivered to a conveying device. This known apparatus has the disadvantage that it takes up a comparatively great amount of space in the vacuum chamber, that it is slow and noisy in operation, that it does not allow the substrate to cool sufficiently, and also that it is not capable of rotating the substrate during the surface treatment and varying its position with respect to the ion source or tilting it.
It is the object of the present invention to create an apparatus of the kind described above, which will not have the disadvantages of known apparatus, will operate quickly and handle the substrates gently, will be very reliable in operation, and will be inexpensive to manufacture.
This object is achieved according to the invention by a substrate support joined to a hollow shaft, a base plate disposed underneath the substrate support, which together with spacing means and a clamping ring or fingers extending approximately parallel to the plane of the substrate support, forms a displaceable cage partially surrounding the substrate support and held coaxial with the substrate support, while the substrate which is introducible through a gap in the side wall of the cage between two spacers can be deposited on the substrate support and can be held there by the clamping ring or the fingers after a relative movement between the substrate support and the cage.
Preferably the hollow shaft bearing the substrate support is provided with passages which at one end correspond with infeed and outfeed lines and at the other end correspond with cooling passages in the substrate support or a chamber formed between the substrate support surface and the substrate.
To permit a precise laying of the substrate on the substrate support surface the cage is displaceable with respect to the substrate support by one or more actuators, e.g., a hydraulic or pneumatic cylinder, or by lifting means equipped with spindle-and-nut drives.
Also provided for this purpose is a loading and unloading arm which can be driven transversely of the longitudinal axis of the hollow shaft into an opening or a slot which is formed by two adjacent spacers, the clamping ring and the bottom plate of the cage, and whose end facing the apparatus is provided with a mounting for the substrate, the mounting having openings through which the lifting pins reach which are disposed on the bottom plate of the cage and thus come in contact with the substrate and ca lift it up or lay it down on the mounting.
The hollow shaft can best be driven through a gear or cogbelt drive by a motor, and for this purpose it is held in a bearing in the housing cover, the housing being mounted for pivoting about a shaft on the frame of the apparatus, which is parallel to the plane of the surface of the substrate support.
Advantageously, the bottom plate is supported on at least one lifting rod or plunger, the lifting rods or plungers being driven by a jack or a mechanically operated lifting device driven by a motor through a cogbelt.
The lifting rod in that case is supported on a two-armed differential lever whose ends cooperate with the connecting rods of cylinders which are inserted into the hydraulic circuit.
To provide for a good cooling of the substrate, the hollow shaft has a plurality of axis-parallel passages which lead into circumferential grooves and/or a central opening, the bottom plate of the cage being provided with openings through which the crown-shaped, cage end of the hollow shaft reaches with its segments, the ends of the segments being fixedly joined to the substrate support.
It is desirable that passages through which a gas cooling the substrate can enter into the interstice or chamber formed at least temporarily by the substrate and the substrate support.